The exemplary embodiments relates to a projector.
FIG. 7 is an explanatory view of a related-art projector 900.
The related-art projector 900 includes: a lighting unit 902; a color-separating and guiding optical system 200 for separating light coming from the lighting unit 902 into lights in three different colors and guiding the respective lights to regions to be illuminated; three electro-optical modulation devices 400R, 400G and 400B for modulating the respective lights in the three colors separated by the color-separating and guiding optical system 200 in accordance with image information; a cross dichroic prism 500 for synthesizing the lights modulated by the thee electro-optical modulation devices 400R, 400G and 400B; and a projecting optical system 600 for projecting the light synthesized by the cross dichroic prism 500. The lighting unit 902 includes: a light source device 910 which has a parabolic reflector 914 and a light emission tube 912 disposed in the vicinity of the focus of the parabolic reflector 914 and emits illumination light; a first lens array 920 having a plurality of first small lenses 921 which divide the illumination light coming from the light source device 910 into a plurality of partial light fluxes; a second lens array 930 having a plurality of second small lenses 931 corresponding to the first small lenses 921; a polarization conversion element 940 for converting entering lights into one type linear polarized lights; and a superposing lens 950 for superposing the respective partial light fluxes coming from the polarization conversion element 940 on the regions to be illuminated (for example, see JP-A-8-304739, FIG. 11).
With the related-art projector 900, the lighting unit 902 is capable of converting light emitted from the light source device 910, which light has comparatively non-uniform in-plane light intensity distribution, into light having comparatively uniform in-plane light intensity distribution, and then supplying the converted light to the liquid crystal panels of the electro-optical modulation devices as the illumination targets by the operation of the first lens array 920, the second lens array 930, and the superposing lens 950.
In recent years, there is an increasing demand for using more compact electro-optical modulation devices for the cost reduction of the projector.
However, in the related-art projector 900, lowering of illumination efficiency and/or non-uniformity of luminance may be caused if the lighting unit 902 is made smaller in accordance with miniaturization of the electro-optical modulation devices. It is therefore impossible to drastically reduce the size of the lighting unit 902. Similarly, there is a limit to miniaturization of the color-separating and guiding optical system 200.
The size of the regions to be illuminated is determined by multiplying the size of the first small lenses 921 by a ratio f2/f1 (enlargement rate, f1: focal length of the second small lenses 931, f2: focal length of the superposing lens 950). It is difficult, however, to reduce the size of the first small lenses 921 without reducing the size of the lighting unit 902. It is also difficult to decrease the focal length f2 of the superposing lens 950 without reducing the size of the color-separating and guiding optical system 200. Furthermore, it is not preferable to increase the focal length f1 of the second small lenses 931 since the lighting unit 902 becomes larger accordingly. It is therefore not easy to reduce the size of the regions to be illuminated. In the result, it is not easy to employ the miniaturized electro-optical modulation devices.
This problem arises not only from the electro-optical modulation devices using the liquid crystal panels, but also from other electro-optical modulation devices.